1. Field of the Invention
This invention relates to a method of forming electrically conductive paths in accordance with a predetermined geometry on surfaces of a substrate.
2. Description of the Prior Art
Substrates with electrically conductive patterns thereon and therein are well known in the prior art. Best known examples of this type are printed circuit boards with electrically conductive patterns formed on the surface thereof by standard techniques of either an additive process or a subtractive process of removing portions of an existing conductor, leaving the desired conductor pattern.
Another form of prior art substrate which combines the additive and subtractive techniques with conductive patterns thereon is shown by Lehtonen (U.S. Pat. No. 3,438,127) wherein a grooved substrate is formed by forming a mold having extensions therein which form grooves in the molded substrate which define an electrically conductive pattern. Electrically conductive material is then placed in the grooves on the substrate. Electroless plating and electroplating are stated to be preferred manners whereby conductive material is placed in the grooves.
The plating techniques described in the above noted patent require many processing steps which result in poor economy as well as the waste of production materials. For example, when the entire surface of the substrate is plated, the electrically conductive materials on the portions thereof other than the grooves must be removed by some type of abrading or other machining process. In this case, the deposited electrically conductive material will be lost. Other techniques require that the substrate be judiciously treated with wax or other anti-plating materials to control the situs of the plating operation. In this case, not only is the additional step of placing the wax or other appropriate material on the substrate required, but, in addition, the wax must later be removed and is not ordinarily economically subject to reuse. Furthermore, the above described techniques do not easily lend themselves to a continuous automatic type of production of substrates with electrically conductive paths thereon.